That depends on which program you mean. Unfortunately, this is not a global shortcut, but every application decides on its own how to implement that. This is why it is not present in the global system shortcuts.

What you can do is to catch the "Alt-Right" combination -- and xbindkeys here, as mentioned in another reply, a way to solve that -- and let it emit "Ctrl-Right". This will achieve using Alt-Right for jumping to the next word. But there is a downside: you will not be able to get rid of the "Ctrl-Right" combination doing the same.

OK, so how exactly does the configuration with xbindkeys looks like. It is much less straightforward than it looks like at first. I tried to do it below, but it turned out to be next to impossible.

First, install xmacro and xbindkeys, and create the rc file for xbindkeys.

What this will do: when you first press Alt-Right, xbindkeys will run the command; but beware! the keys alt and right are still pressed. We must "unpress" them first. The above works, but not perfectly, be warned. Most importantly, to jump two words, you have the press the combination, release it, and press again; with ctrl-right, you can press the combination, and then repeat the press on the right arrow as many times as needed.